Horizontally-opposed dual four-cylinder engines with common rotary valves, certainly is a mouthful. But that is exactly what Finley Robinson Porter had finished designing only a little over a year after he left Mercer, as the Chief Engineer where he designed the legendary T-head Raceabout. This pair of engines was intended for aircraft use, and each was to be equipped with a propellor. At this point, it is unknown if this project ever went past the drawing stage, but it certainly is interesting to study his work.
We were fortunate to be able to talk with Porter’s Great Granddaughter recently and learned of this concept and its drawings. After studying them we are amazed by the vision that this man had and his ability to be able to see this concept through to its final design and drawings. It came right on the heels of the exceptional F.R.P. car he designed and built with a s.o.h.c. 454-c.i.d. four-cylinder engine that was right on the cutting edge at the time.
Just above at the top is a cross-sectioned end view of a pair of cylinders, and it shows one of the rotary valves located top and bottom on ball bearings. The intake charge enters the valve at (2) on the middle bottom and exhausts out of the top of it. The valve supply chamber (4) communicates with the feed (1) from the intake manifold and has opposed cylinder supply ports (6 and 7 – see photo at the top of the post) opening through the face of the valve.
The exhaust chamber (5) communicates with the upwardly extended tubular portion (2) that also has opposed exhaust ports (8 and 9 – see photo at the top of the post) opening through the face of the valve. The rotary valve is tapered and is smaller at the bottom than at the top. The fuel supply for the cylinders is drawn in through the bottom of the valve, and the exhaust gases are discharged through the top of the valve.
The two detail photos above show more of the construction. The left-hand drawing shows the intermediate gear (48) that is driven by a gear on the two joined-driveshafts (38). It in turn drives shaft (46) that operates the four rotary valves and gear and shaft (55) that drives the magneto on the left (52) and the water pump on the right (53). The right-hand drawing shows the details of the gears (49 and 50) that turn the rotary valve and also shows the combustion chamber. The updraft intake manifold (70) can be seen in the bottom center photo.